cd658a30ef
- async closure Output deduction, solver cycle step kinds from the goal source, object supertrait projections, impl candidate merging, trait supertrait well-formedness, E0282 for casts and method calls on diverging variables, the (..) tuple pattern Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
32 lines
1 KiB
Rust
32 lines
1 KiB
Rust
// An `AsyncFn(&str) -> &str` bound gives the async closure's body its return type with the
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// closure's own late-bound region (rustc coroutine-closure `return_ty`); the closure must be
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// accepted and run.
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use std::future::Future;
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use std::pin::pin;
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use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
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fn noop_raw() -> RawWaker {
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fn clone(_: *const ()) -> RawWaker { noop_raw() }
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fn noop(_: *const ()) {}
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static VT: RawWakerVTable = RawWakerVTable::new(clone, noop, noop, noop);
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RawWaker::new(std::ptr::null(), &VT)
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}
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fn block_on<F: Future>(f: F) -> F::Output {
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let waker = unsafe { Waker::from_raw(noop_raw()) };
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let mut cx = Context::from_waker(&waker);
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let mut f = pin!(f);
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loop {
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if let Poll::Ready(v) = f.as_mut().poll(&mut cx) { return v; }
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}
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}
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async fn call(f: impl AsyncFn(&str) -> &str) -> usize {
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f("hello").await.len()
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}
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#[test]
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fn ref_output() {
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assert_eq!(block_on(call(async |x| x)), 5);
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assert_eq!(block_on(call(async |x: &str| { let y = x; y })), 5);
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}
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